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UNITED STATES PATENT OFFICE.

GEORGE D. VAN ABS DALE AND CHARLES G. MAIER, OF NEW YORK, N. Y.

PROCESS OF EXTRACTING MANGANESE AND MAKING SULFURIC ACID AND MANGANESE DIOXID.

No Drawing.

To all whom it may concern.

Be it known that we, GEORGE D. VAN Ans- DALE and CHARLES G. Mama, citizens of the United States, and residents of New York city, in the county of New York and State of New York, have invented certain new and useful Improvements in Processes of Extracting Manganese and Making. Sulfuric Acid and Manganese Dioxid, of which the following is a specification.

The hereinafter described process is a rocess of extractin man anese from its ores, particularly those in which the manganese occurs as dioxid, producing as final products pure manganese dioxid, and sulfuric acid.

Many dioxid ores of manganese contain impurities which render them useless for certain purposes. For example, certain manganese ores contain small'amounts of copper, the presence of which in more than traces in most cases renders the ore unsuitable for battery purposes. Iron is also objectionable for some uses. It is also true that while manganese ores are not uncommon, it is only in a few localities that they occur of a sufiiciently high grade to bear shipping charges and still permit their bein sold at a profit under normal conditions.

The object of this invention is to provide a means by which a pure, high-grade manganese dioxid can be made, suitable for all purposes, particularly from dioxid ores low in grade or having objectionable impurities.

Another object and result of this invention is to produce simultaneously with the diox'id of manganese anequivalent of sulfuric acid.

The following equations represent substantially the reactions of the process:

II. MnSO +2H O electrolyzed:

nese dioxid at the anode and an equivalent Specification of Letters Patent.

Patented May 20, 1919.

Application filed April 18, 1918. Serial N 0. 229,465.

of free sulfuric acid corresponding to the above equation (11) together with an equivalent of free hydrogen at the cathode, these reactions together forming a new and useful method of leaching manganese di-oxid ores, precipitating pure manganese dioxid from the resulting solution by electrolysis, and simultaneously producing free sulfuric acid.

This invention may be practically carried on in a number of ways, one of which will be described. 1

The ore, preferably containing most of its manganese as dioxid, is ground to a suflicient degree of fineness as determined by its characteristics with respect to leaching The ground ore is then suspended in water and agitated, which may be done in any suitable apparatus, and sulfur dioxid is applied in such a way and the agitation continued so as to obtain th greatest efficiency of the S0 and the best solvent action on the ore.

If concentrated S0 is used for this purpose, it will be found that considerable evolution of heat occurs due to equation (I) above being exothermic. This is not objectionable since heated solutions are preferably used in the next step of the process. 1 Also less amounts of the objectionable thionate compounds of manganese are produced by leaching hot. p I

After complete extraction of the soluble manganese takes place, the leached ore is gold or silver, these will remain with the leached residue. from which they may be extracted by any usual method.

Ores containing oxidized copper compounds will. in most cases, yield such copper to the solvent action of S0 and any such dissolved copper may, if desired. be precipitated from the solution in any suitable way- Since manganous sulfate is very soluble in water, practically any desired strength of solution'may be made. This will depend on various conditions. For example, when an ore is subjected to the above leaching treatment in the maximum ratio of ore to 1 liquid that is convenient and the resulting solution does not carry enough manganese, the leached orc may be separated from the solution. fresh ore added to the solution and agitation and application of sulfur dioxid renewed. In this way solutions of manganous sulfate of any strength desired may be made, which is a considerable practical advantage.

Some possible constitutents of the above solutions made as described may be objectionable in the succeeding step of electrolysis, for example ferrous iron, and they may be rendered harmless in any suitable manner. For example ferrous iron may be oxidized to ferric iron in which state it does not interfere.

A solution of manganese made as above described will also usually contain salts of manganese other than the sulfate, for example thionates. These sulfur compounds, other than the sulfate, are objectionable in electrolysis, and they should accordingly be either removed or converted into other compounds. One way of doing this is to heat the solutions to boiling after adding sulfuric acid, whereby the thionates are decomposed and converted into sulfates, and free $0 The solution, now containing substantially only manganous sulfate, is then subjected to electrolysis, which may be carried on with any electrodes and apparatus suitable for the purpose. We have found that graphite or carbon is suitable as electrodes, although other kinds of electrodes maybe used.

Crushed coke or carbon may also be used as an anode material in case the presence of carbon is not objectionable in the finished manganese dioxid product, and in certain cases working in this way may make a desirable roduct for certain uses.

Suitable conditions for electrolysis under the present process are: A current density from ten to twenty-five amperes per square foot, from ten to fifteen amperes per square foot giving maximum deposition efficiency at the anode, the potential drop varying from about 2. at ten amperes per square foot to about 3. at twenty-five amperes per square foot. The electrode distances for the above conditions may be from one to two inches surface to surface.

We have found that neutral solutions of manganous sulfate give a yield of dioxid with high current efiiciency over a range from nearly concentrated solutions down to a percentage of about 0.5 Mn. We have also found that the current efficiency varies more or less inversely in proportion to the amount of free acid present when the electrolysis is carried on at ordinary temperatures, and we have also found that the current efficiency becomes reduced to an average of less than 30% when the amount of acid reaches about 10% free H SO This is a serious practical difficulty since, starting with a neutral solu; tion, as this is elect olyzed, sulfuric acid accumulates.

We have, however, discovered that the application of'heat completely neutralizes this injurious effect caused by the accumulation of free acid. For example, solutions containing about 15% free acid when electrolyzed at ordinary temperatures give extremely low and uncommercial current efficiencies, while the same solutions heated to say Crgive over 90% current efiiciencies as measured by the amount of deposited manganese dioxid.

Furthermore, when heated such a solution, carrying large amounts of manganous sulfate, may be electrolyzed at a high uniform current efficiency, continuing at this figure until the solutions are nearly exhausted. For example, such a solution gives still 90% efliciency when containing only 0.6% Mn.

This .is a very important practical advantage, since by Working in this way a strong solution of manganous sulphate containing some acid may be electrolyzed until practically all of the manganese is removed, and there remains substantially pure sulfuric acid.

N e have also found that working with a heated solution has the additional important practical advantage that practically chemically pure manganese dioxid is deposited, which is important for many uses of the product.

We have further found that manganese dioxid deposited under the above mentioned conditions by this process, is. deposited in a physical form which is very desirablefor some uses. For example, the ideal form of a depolarizer for battery use is one having a maximum surface." ,A natural product, such as the high grade dioxid ores heretofore used for this purpose, is of a granular nature, and therefore the possible increase of surface by fineness of grinding soon reaches a limit due to the fine particles packing together. In other words, a product having a flaky structure would be ideal for the purpose andthe dioxid'produced by our process may be made of such a flaky character, and we have also found that by interrupting the deposition at intervals, a product may be made of any degree of thickness desired, from flat pieces of an appreciable thickness down to. extremely thin flat flakes. If an insoluble anode is used wh 3e conductivity is much greater than that of the MnO deposited at the anode, then the dioxid detaches itself automatically in the form of very thin flakes which float in the electrolyte and may be subsequently recovered by filtration. An example of such an anode is platinum.

We have also discovered that when graphite is used as an anode, a considerable thickness of dioxid may be plated out before detachment, and, further, when plated out on graphite under suitable conditions, it adheres strongly to the graphite, forming a dense deposi This deposit can be detached from the anode in several ways. For example, a reversal of the direction of the current and at the same time an increase in the density of the same, results in a detachment of the deposit" from the electrode. Obviously any desired thickness of the dioxid may be made in this way.

The electrolysis maybe carried out in any way desired. or to the removal of any amount of manganese, depending on the use to which the acid produced is to be put.

The electrolyte, after removal of the major part of the-manganese, consists of substantially pure sulfuric acid, which may be concentrated in the usual way and used for any purpose to which it is adapted. It will under ordinary conditions probably not be commercially desirable to collect and utilize the hydrogen evolved at the cathode and this will therefore be allowed to escape as formed.

The manganese dioxid when made under proper conditions, as described, will contain no oxid of manganese other than the dioxid, but will in some cases contain water of hydration. For certain purposes this may be desirable, since such a product will have more surface per unit of weight of manganese than a dry product. For such uses the product may be separated by filtration and washing, or otherwise, from the electrolyte adhering to it, and dried for the removal of hygroscopic moisture.

I or other purposes the removal of the water of hydration may be-desirable, and

for such uses the dioxid after washing may be heated until the water of hydration is driven oif.

For ores in which most of the manganese is present as dioxid, water alone may be used for the first step of the process. If, however, ores are treated containing oxids Other than the dioxid, sulfur dioxid alone will not give a high recovery, since these other oxids are not completely dissolved by $0,. In such a case, an addition of a part of the acid produced from the electrolysis in amount sufficient to dissolve the other oxids maybe made to the pulp in the first step, and the result of the combined action of the gas and the acid added will be an extraction of practically all of the manganese. In general we have found that an addition of acid equivalent to the MnO present in the ore is sufficient to give practically a complete extraction, the MnO being dissolved b v the action of the S0 Having thus described the invention, what is claimed as new is:

1. A process of extracting manganese a d making sulfuric acid and manganese dioxid, which consists in dioxid gas into the I originally present,

suspending ground manganese ore in water, adding acid to dissolve oxids ofmanganese other than the dioxid, agitating and introducing sulfur pulp, and continuing to agitate while still conducting sulfur dioxid gas into the pulp, until substantial completion of the reaction between the sulfur dioxid and the manganese compounds contained in the ore, separating the resulting solution containing manganese from the leached ore residue, removing undesirable constituents of the solution, heating the mangan esesolution, and subjecting the heated manganese solution to electrolysis, making this electrolysis discontinuous as to the anode so asto produce desirable physical qualities in the separated manganese-dioxid, continuing the electrolysis to obtain a sufficient degree ofpurity and strength of the sulfuric acid produced and to obtain as dioxid a sufficient amount of the manganese removing the substantially manganese free sulfuric acid thus produced, and in then removing the precipitated manganese dioxid from the anode.

2. A step in a'process of extracting manganese and making sulfuric acid and manganese dioxid, which consists in suspending ground manganese ore in water, adding acid to dissolve oxids of manganese other than the dioxid, agitating it, introducing sulfuric dioxid-gas into the pulp, and continuing this agitation While still conducting sulfur dioxid into the pulp until substantial com pletion of the reaction between the sulfur dioxid and the manganese compounds contained in the ore.

3. The steps in a process of extracting manganese and making sulfuric acid and manganese dioxid, which consists in subjecting a pulp of the manganese ore to the action of sulfur dioxid and se arating the resulting manganese solution rom the leached ore residue.

4. A ste in a process of extracting manganese and making sulfuric acid and manganese dioxid, which consists in oxidizing the ferrous iron content to ferric iron and removing by precipitation manganese thionates from a manganese solution as a preliminary to electrolysis.

5. A step in a process of extracting manganese and making sulfuric acid and man-' ganese dioxid, which consists'in heating a manganese sulphate solution during electrolysis.

I 6. A step in a process of extracting manganese and making sulphuric acid and manganese dioxid, which consists in subjecting a heated manganese solution to electrolysis, andimaking this electrolysis discontinuous as to the anode, so as to produce desirable ,physical qualities in the. separated inanganese dioxid. 7. step in a process of extracting manganese and making sulfuric acid and manganese dioxid, which consists in electrolyiing a heated solution of manganese, continuing the electrolysis until the resulting sulfuric acid is substantially free from manganese, and removing the substantially manganese-free sulfuric acid.

8. A step in a process of extracting manganese and making sulfuric acid and manganese dioxid, which consists in removal of deposited manganese dioxid from an anode by reversing the current used for electrolysis,

and at the same time increasing the current density.

9. A process of extracting manganese and making sulfuric acid and manganese dioxid, which consists in suspending ground manganese ore in water, adding acid to dissolve oxids of manganese other than the dioxid, in treating the mixture with sulfur dioxid to form a solution of manganous salts, in separating the solution thus formed, purifying this and in treating the solution by electrolysis to obtain manganese dioxid and sulfuric acid.

10. A process of extracting manganese and making sulfuric acid and manganese dioxid, which consists in treating a ground manganese ore in suspension in water with sulfur dioxid to form a solution of manganous salts, adding acid to dissolve oxids of manganese other than the dioxid in separating the solution thusformed from the ore remaining, purifying the same, and in treating the solution by electrolysis while the solution is hot, to form manganese dioxid and sulfuric acid.

11. A step in a process of extracting man ganese and making sulfuric acid and manganese dioxid, which consists in suspending.-

ground manganese ore in water, agitating the pulp thus produced, introducing sulfur dioxid gas into the pulp and during such introduction continuing the agitation and until substantial completion of the reaction between the sulfur dioxid and the manganese content of the ore.

12. A process 0 extracting manganese and making sulfuric acid and manganese dioxid, which consists in preparing a pulp of the manganese ore in water, treating the pulp with sulfur dioxid to bring the manganese content into solution as a sulfate, separating the solution thus produced, and electrolyzing the solution whereby to obtain manganese dioxid and sulfuric acid.

13. A process of extracting manganese and making sulfuric acid and manganese dioxid, which consists in preparing a pulp of manganese ore, treating thepulp With sulfur dioxid to bring the manganese content of the ore into solution as a sulfate, separating the solution from the leached ore, heating the solution, and electrolyzing the solution while hot.

Signed at New York City, in the county of New York and State of New York, this 12th day of April, A. D. 1918.

GEORGE l). VAN ABSDALE. EL. 8-] CHARLES e. MAIER. 1. 3.

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